Multi-cluster gear device

ABSTRACT

A multi-cluster gear device operable to function as a pump, a motor or operable to alternate between a pump and a motor.

FIELD OF THE INVENTION

The invention relates to a multi-cluster gear device and more particularly to a multi-cluster gear hydraulic device that can operate as a pump or motor.

BACKGROUND OF THE INVENTION

In general, gear pumps and motors use a combination of two gears as a mechanical device to cooperate with the transfer of fluid between one fluid inlet to one fluid outlet of the device. In order to do mechanical work, gear motors receive pressurized oil which flows around the gears. The pressurized oil cannot flow through the gears at the point where they are meshed and therefore the oil flows around the outside of each of the gears causing the gears to rotate and therefore work. Accordingly, power obtained from the flow of hydraulic fluid through the hydraulic gear device is transferred to rotational power of the shaft connected to one of the gears, thus providing for a gear motor that transforms hydraulic fluid power into rotational power. Alternatively, hydraulic gear devices are often used in hydraulic fluid power applications such as in transmissions, power steering and engines, such that power obtained from rotation of a shaft connected to one of the gears is transferred to fluid power causing the flow of hydraulic fluid through the pump from the fluid inlet to the fluid outlet, thus providing for a gear pump that transforms rotational shaft power into hydraulic fluid power. It is recognized that hydraulic gear devices can be external gear devices, in which the gears are both external, or internal gear devices, in which one gear is external and one is internal.

Gear pumps work on the principal of positive displacement. This means that a constant amount of fluid is pumped during each gear revolution. In general, as the meshed gears in a gear pump rotate they create a low and a high pressure side. Which side is which is determined by the gear rotational direction. Fluid is drawn into the low pressure side, or intake side, of the pump. The fluid is carried by the gears, to the discharge side of the pump. As the gears connect, or mesh, at the discharge side, the fluid is displaced and leaves the pump.

Traditional gear pumps use a pair of gears to draw and deliver fluid between one fluid inlet and one fluid outlet, such that the fluid output is dependent on the size and rotational speed of the gears. In order to deliver a higher output flow of fluid, higher shaft RPM, larger gears or more pumps (e.g. in parallel) are required. However, increasing the number of pumps can increase the number of independent components being used which can result in having more parts that may require maintenance and/or replacement, as well as increased space and weight requirements. Alternatively, the size of the working gears may be increased to increase the output flow, however, this can present a challenge if space is limited, as well as present inertia issues for changing pump speeds. As well, higher rotational speeds can result in higher operational temperatures and overall increased friction and associated costs.

Further, shifting of gear alignments (e.g. axially, laterally) within the housing of the gear pump, during higher hydraulic loadings, can cause undesirable damage (e.g. abrasive wearing of surface material) to the inside surface of the gear housing and/or the gear teeth themselves, as gap tolerances between the gear teeth and the housing inside surface are minimized (e.g. to within one thousandth of an inch) to inhibit hydraulic fluid blow-by from the high pressure side to the low pressure side of the pump. In particular, removal of the surface material due to wear can also increase the gap distance between the gear teeth and the housing inside surface, which can result in decreased pumping efficiency due to increased blow-by of hydraulic fluid from the high pressure side of the pump to the low pressure side of the pump. Further, excessive tension forces can be experienced by fasteners used to assemble multi-piece housings, due to high fluid pressures, which can result in fastener failure and/or undesirable increases in predefined tolerance gaps within a gear cavity of the device.

SUMMARY OF THE INVENTION

It is therefore desired to provide a gear pump and/or motor that is capable of providing variable output flow while using a number of gears that is not equal to the number of hydraulic fluid ports.

It is an object of the present invention to provide for a hydraulic gear device that has greater number of fluid ports communicating with a gear cavity than the number of gears positioned within the gear cavity.

It is an object of the present invention to provide for a hydraulic gear device that obviates or mitigates at least one of the above-presented disadvantages.

The present invention provides a multi-cluster gear device.

In one embodiment, the multi-cluster gear device comprises a shaft rotatable about a longitudinal axis, a primary gear mounted on the shaft, at least two secondary gears spaced about and positioned to engage with the primary gear, each of the at least two secondary gears configured to independently receive fluid from a fluid reservoir and to allow flow of a portion of the fluid about the secondary gear and to allow the remaining portion of the fluid to be carried by the primary gear to the adjacent secondary gear.

In a further embodiment, the multi-cluster gear device includes at least two secondary gears, the secondary gears being smaller than the primary gear. In a further embodiment the at least two secondary gears are spaced evenly about the periphery of the primary gear.

In a further embodiment, 50% of the fluid received by each of the at least two secondary gears flows around respective secondary gears and the remaining 50% is carried to the adjacent secondary gear by the primary gear.

In a further embodiment, each of the secondary gears is independently fluidly connected to a fluid inlet and a fluid outlet. In one embodiment, each of the secondary gears is configured to receive fluid at low pressure through the fluid inlet.

In one embodiment, each of the secondary gears is configured to release fluid at high pressure through the fluid outlet.

In an alternative embodiment, the multi-cluster gear device includes three secondary gears. In another embodiment, the multi-cluster gear devices includes four secondary gears.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described in further detail with reference to the following figures:

FIGS. 1A and 1B are examples of a prior art conventional two-gear pump;

FIG. 2 is a schematic of one embodiment of the multi-cluster gear device of the present invention, showing a three gear cluster configuration;

FIG. 3 is one embodiment of a portion of the multi-cluster gear device of the present invention, showing a five gear cluster configuration, in isolation;

FIG. 4 is a partial cut away of an alternative embodiment of the multi-cluster gear device of the present invention, having a three pump via a four gear cluster configuration;

FIG. 5 is a sectional view of the embodiment of FIG. 4, showing the three pump configuration in isolation;

FIG. 6 is a perspective view of the multi-cluster gear device of FIGS. 4 and 5 within a housing;

FIG. 7 is an alternative embodiment of the multi-cluster gear device of FIG. 6 shown in a hoisting operation application;

FIG. 8 is a partial cut away view of one embodiment of the four pump configuration of the multi-cluster five gear device of the present invention, showing an internal gear configuration;

FIG. 9 is an example of the hydraulic circuitry of a four pump, external cluster gear device;

FIG. 10 is a schematic of a bypass loop, of an external gear pump arrangement, that may be used in the multi-cluster gear device described herein;

FIG. 11 shows one embodiment of the use of the multi-cluster gear device wherein two devices are mechanically connected to one common shaft;

FIG. 12 shows an alternative configuration of the gear device of FIG. 1;

FIG. 13 shows an alternative configuration of the gear device of FIG. 12;

FIG. 14 a shows a configuration of the gear device of FIG. 12 with a predefined tolerance;

FIG. 14 b shows a configuration of the gear device of FIG. 12 with a predefined tolerance reduced due to movement of the gear;

FIG. 15 shows an exploded view of the gear device of FIG. 12;

FIG. 16 shows a further unassembled view of the gear device of FIG. 12;

FIG. 17 shows a further unassembled view of the gear device of FIG. 12;

FIG. 18 shows an alternative configuration of the gear device of FIG. 12;

FIG. 19 shows a expanded view of a mounting mechanism of the gear device of FIG. 18;

FIG. 20 shows an alternative configuration of the gear device of FIG. 12;

FIG. 21 shows an alternative configuration of the gear device of FIG. 12;

FIG. 22 shows a side view of the gear device of FIG. 20;

FIG. 23 shows a half exploded view of the gear device of FIG. 20;

FIG. 24 shows an alternative configuration of the gear device of FIG. 12;

FIG. 25 shows a half exploded view of the gear device of FIG. 24;

FIG. 26 shows a half assembled view of the gear device of FIG. 24; and

FIG. 27 shows a further embodiment of the gear device of FIG. 22.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention provides a multi-cluster hydraulic gear device that includes a main gear (e.g. a large gear) fluidly connected to at least two secondary gears (e.g. a first small gear and a second small gear). Each gear cluster, i.e. the mechanical meshed connection between adjacent gears (e.g. of the main gear with the secondary gear), is fluidly connected to an adjacent gear cluster (e.g. connection of the main gear with the other secondary gear) and is able to, in one working mode, defer 50% of the drawn fluid to the downstream secondary gear (e.g. second small gear) while also receiving 50% from the upstream secondary gear (e.g. first small gear).

The present invention will now be described in further detail with reference to FIGS. 1-11 in which the multi-cluster hydraulic gear device is indicated generally at numeral 20. The multi-cluster hydraulic gear device 20, described herein, may be utilized in any arrangement that requires the use of a gear pump or motor. In use as a gear pump the device provides a means for fluid to be drawn from a fluid source, e.g. tank, and force it to and or through a flow/pressure control device or fluid sink. Examples of the types of applications in which the multi-cluster hydraulic gear device, described herein, may be used include, but are not limited too, primary or secondary brake systems that may be used on, for example, a vehicle such as a truck or rail car, or in commercial non-vehicular applications such as in mining equipment, elevator equipment, oil drilling equipment and other stationary applications.

The present invention provides a multi-cluster hydraulic gear device that includes a main drive gear, also referred to herein as a large or primary gear, and at least two additional secondary gears (e.g. each smaller than the main gear). In one embodiment, fluid is drawn into a low pressure cavity of the device where it is split into two or more parts. One follows the rotation of one of the secondary gears into the high pressure cavity of the same cluster while a second part of the flow follows the rotation of the main gear into the high pressure side of the next nearest cluster (between the next secondary gear and the main gear) as per the main gear's rotation direction. The multi-cluster hydraulic gear device is able to operate in a working (e.g. full flow) mode and also in a by-pass mode, both modes are discussed further below.

The multi-cluster hydraulic gear device can include a ring gear, or large gear, having internal or external teeth, that is supported within a housing. One or more spur gears, or pinion gears, also referred to herein as small/secondary gears, include external teeth, that are sized to mesh with the teeth of the large gear. For a main gear having internal teeth, each of the secondary gears is located internally of the main gear. For a main gear having external teeth, each of the secondary gears is located externally of the main gear. The teeth on each secondary gear are sized to mesh with the teeth on the main gear. Rotation of the main gear will initiate rotation of each of the secondary gears, and vice versa, i.e. each of the gears can be driving or can be driven. It is recognized that the main gear can be of a diameter greater than any one or all of the secondary gears. It is recognized that the main gear can be of a diameter smaller than any one or all of the secondary gears. It is recognized that the main gear can be of the same diameter as any one or all of the secondary gears.

Due the presence of two or more secondary gears, each of these gears acts as a gear device (e.g. pump or motor), also referred to as a gear cluster, due to the individual interaction of each secondary gear with its respective portion of the main gear as a respective gear cluster of the multi-gear cluster. Accordingly, it is recognized that the multi-cluster hydraulic gear device 20 contains multiple gear devices (e.g. pump or motor) within a common housing, such that each of the gear devices contributes a respective portion of the total hydraulic fluid output of the multi-cluster hydraulic gear device 20. It is also recognized that each gear device of the multi-cluster hydraulic gear device 20 can have a pair of hydraulic ports (e.g. an inlet port and an outlet port) associated therewith, such that each port communicates hydraulic fluid between an exterior of a gear cavity containing the multiple gear devices and the interior of the gear cavity. This configuration of ports can result in a greater number of fluid ports communicating fluid to and from the gear cavity than the number of actual gears positioned within the gear cavity. In one embodiment, there can be a pair of hydraulic ports associated with each of the secondary gears, however it is recognized that there can be more than two ports per secondary gear in the case of multi-port configurations. For example, each secondary gear can have two inlet ports and two outlet ports associated therewith, as desired. Alternatively, the number of inlet ports and outlet ports per secondary gear can be unequal (e.g. an inlet port with a pair of outlet ports or a pair of inlet ports with an outlet port).

Turning to FIGS. 1A and 1B, an embodiment of a prior art, conventional, gear pump 10 is shown having two gears 12. This conventional two gear pump 10 delivers approximately 50% of its output flow via one gear 12 and the other approximately 50% through its mated gear 12 to create close to total 100% output. The gear pump 10 draws in fluid at the low pressure side of the pump 10. The total amount of the fluid that is drawn into the gear pump 10, i.e. 100%, is then divided in two by rotation of the gears 12. 50% will flow around one of the gears 12 and 50% about the other gear 12, as shown by the arrows. As stated above, the fluid is inhibited from passing between the gears 12 at the point where they are meshed. Each of the separate 50% fluid flows will then rejoin at the outlet of the pump 10, i.e. the high pressure side, shown at arrow A in FIG. 1B. It will be understood that, in general, while a theoretical pump 10 will deliver a portion (e.g. 50%) via one gear 12 and the remaining portion(s) (e.g. 50%) through its mated gear(s) 12 to create 100%, with zero leakage, the actual real application may not achieve 100% output, as stated above.

The configuration of the individual gears used within the multi-cluster hydraulic gear device 20 will now be described. Turning now to FIG. 2, a schematic is provided showing one example of the multi-cluster hydraulic gear device 20 of the present invention. It should be noted that the multi-cluster hydraulic gear device 20, described herein, may also be referred to as a multi-cluster hydraulic gear pump or motor. As seen in FIG. 2, the multi-cluster gear device 20 includes a main (e.g. internal large) gear 22 coupled to two secondary (e.g. small) gears 24. The main gear 22 includes internal teeth, not shown, that mesh with the external teeth, not shown, on the secondary gears 24. The meshing of the teeth is shown clearly in the embodiment illustrated in FIG. 3, for example.

The rotational direction of the main gear 22 and the secondary gears 24A, 24B, is shown by the arrows in FIG. 2. In this embodiment, all the gears turn in the same direction and at the same rotational rate (e.g. angular gear or tooth velocity). It will be understood that in one mode of operation, the main gear 22 drives the secondary gears 24A and 24B, as the main gear 22 can be connected to an external drive shaft—not shown—that is mechanized to force rotation of the main gear 22. In an alternate mode, the secondary gears 24A and 24B can drive the main gear, as the secondary gears 24A,B can be connected to respective external drive shafts—not shown—that are mechanized to force/drive rotation of the secondary gears 24. Alternatively, one of the secondary gears 24A or 24B can drive the main gear, as the one secondary gear 24A or 24B can be connected to a respective external drive shaft—not shown—that is mechanized to force/drive rotation of the one secondary gear 24A or 24B. In any event, it is recognized that there are two or more gear devices 23 within a gear cavity 25 of a housing 42 of the multi-cluster hydraulic gear device 20. Again it is recognized that each of the gear devices 23 is considered one gear cluster of the multi-cluster hydraulic gear device 20, whereby one gear cluster provides for the meshing of teeth between a respective portion of the teeth of the main gear 22 with teeth of the respective secondary gear 22.

In operation of the multi-cluster hydraulic gear device 20 of FIG. 2, hydraulic fluid is drawn into the multi-cluster gear device 20 at a low pressure side of the main gear 22 and secondary gear 24A, indicated at fluid inlet port A, such that a portion (e.g. 50%) of the drawn fluid from the reservoir 27 flows around the secondary gear 24A while the remaining portion (e.g. 50%) of the drawn fluid is carried by the main gear to the next nearest secondary gear 24B, as shown by the directional arrows. Fluid is also drawn from the reservoir 27 into the gear pump 20 at a low pressure side of secondary gear 24B and main gear 22, indicated at fluid inlet port B, and a portion (e.g. 50%) flows around secondary gear 24B while the remaining portion (e.g. 50%) is carried to secondary gear 24A. The portion (e.g. 50%) that is carried from secondary gear 24B to 24A combines with the portion (e.g. 50%) volume that has come around with the secondary gear 24A to output at 100% at a high pressure side of the secondary gear 24A and the main gear 22, as indicated at fluid outlet port C. Likewise the portion (e.g. 50%) that is carried from the secondary gear 24A to 24B combines with the portion (e.g. 50%) volume that has come around with the secondary gear 24B to output at 100% at a high pressure side of secondary gear 24B and main gear 22, as indicated at fluid outlet port D. It should be noted that each gear device 23 has both a low pressure port and a high pressure port that communicates fluid into/out of the gear cavity 25 common to all gear devices 23. Each pump 20 has therefore deferred a portion (e.g. 50% flow) to the downstream secondary gear while receiving a portion (e.g. 50% flow) from the upstream secondary gear. The combined total output flow (as the combined portions) of the two secondary gears 24A,B is equivalent to the output of two pump pairs (e.g. gear devices 23), but the multi-cluster hydraulic gear pump 20 configuration only uses three gears for the output, whereas two separate pumps requires four individual gears (i.e. two for each pump). It is recognized that the multi-cluster hydraulic gear pump 20 has less number of clustered gears than double that of the number of gear devices 23 (e.g. three gears for two gear devices, four gears for three gear devices, etc.). This provides that the multi-cluster hydraulic gear pump 20 that has fewer numbers of gears than more traditional two gear pumps (see FIG. 1A), which can result in overall reduced gear noise, gear friction and wear, as well as reduced gear parts (e.g. shafts, bearings, etc.) and cost.

Turning to FIG. 3, an alternate configuration of the multi-cluster gear device 20 is shown. In this embodiment, the multi-cluster hydraulic gear device 20 includes a main (e.g. internal large) gear 22 and a four secondary (e.g. small) gears 24. The secondary gears 24 are spaced around the (e.g. internal) surface of the main gear 22 at equal spacings in the Figure, however the relative spacing of the secondary gears to one another can differ in length and the secondary gears can be placed at preferred unequally spaced locations about the periphery of the main gear 22 depending on the use and/or application. The teeth 26 (e.g. external) on each of the secondary gears 24 are configured to mesh with the teeth 28 (e.g. internal) of the main gear 22 as the main gear 22 and secondary gear 24 rotate, thus defining each of the respective gear devices 23 as the respective gear clusters of the multi-gear cluster environment in the common gear cavity 23 of the multi-cluster hydraulic gear device 20. The main gear 22 and the secondary gears 24 are held in a meshed configuration and are positioned inside the common gear cavity 23 of the device case, or housing. It will be understood that each of the secondary gears 24 can be held at a predefined distance (e.g. gear center to center distance) from the main gear 22 that allows for meshing of the teeth 26 with the teeth 28 (direct contact there-between) whilst also allowing for rotation of the secondary gears 24, being driven by the rotation of the main gear 22, or vice versa. Further, the positioning of the main gear 22 and the secondary gears 24 can provide for fluid flow between adjacent secondary gears 24 via the main gear 22. It will be understood that the positioning of the main gear 22 and secondary gears 24 are not held so as to prevent rotation thereof.

In an alternative embodiment, shown in FIG. 4, the main gear 22 includes external teeth 32 that mesh with external teeth 34 located on each of the secondary gears 24. It will be understood that the difference between these two embodiments (FIGS. 3 and 4) includes the fact that in the embodiment shown in FIG. 3 the main gear 22 and secondary gears 24 all rotate in the same direction. However, in the embodiment shown in FIG. 4, the secondary gears 24 rotate in the opposite direction to the main gear 22. However, the overall function of the multi-cluster hydraulic gear device 20 is the same, irrespective of the direction of fluid flow or main gear or secondary gear rotation.

FIG. 4 illustrates an alternate embodiment of the multi-cluster hydraulic gear device 20 described herein. In this embodiment, the device 20 includes a main larger central gear 22 with three smaller secondary gears 24, located about the periphery of the main gear 22, such that each of the secondary gears 24 meshes with a portion of the teeth of the main gear 22. While only two small gears 24 can be seen in FIG. 4, it will be clear from FIG. 5 that the embodiment illustrated in FIG. 4 includes three secondary gears 24. Each of the secondary gears 24 include (e.g. external) teeth that mesh with the (e.g. external) teeth located on the main gear 22. At least a pair of hydraulic fluid ports 40 (e.g. an inlet and an outlet port) are positioned at each meshing point of the two meshing gears, in other words for each gear device 23. Each of the ports 40 is operable to act as either an inlet or outlet for hydraulic fluid flow either into or our of the common gear cavity 25. It will be understood that when the multi-cluster hydraulic gear device 20 acts as a pump, fluid is drawn by each of the inlet ports 40, when the device is active. Conversely, when the multi-cluster hydraulic gear device 20 is used as a motor, external fluid pressure is applied to one side of one of the port pairs, or multiple pairs, to increase HP and torque, depending on the preferred vehicle travel direction. For example, referring to FIG. 2, fluid pressure may be applied at the port identified at arrow A or at arrow C. In any event, it is recognized that each of the gear devices 23 has a pair of ports 40 associated therewith, consisting of at least one inlet port and one outlet port for the pair.

The multi-cluster hydraulic gear device 20 is housed in a housing, identified at numeral 42 in FIG. 4, which encloses the gears 22, 24, bearings 41 upon which shafts 44,39 of the gears 22, 24 are mounted, wear plates 43, ports 40 and other mechanical components. It will be understood that the housing 42 may be any size and/or shape provided that it encases all the components of the multi-cluster hydraulic gear device 20 in the common gear cavity 25. The size and/or shape of the housing 42 may be governed by the internal components and also the application within which the multi-cluster hydraulic gear device 20 is to be used. FIG. 4 is an example of a split housing having one or more housing portions.

Also shown is a input shaft 44 of the multi-cluster hydraulic gear device 20 which accepts or delivers rotational torque to the main gear 22. The device 20 may also include a shaft seal 47, as well as other seals (not shown) as part of the housing 42, to withstand low pressure and retain hydraulic fluid within the device housing 42. It will be understood that the multi-cluster hydraulic gear device 20, when used as a gear pump, may also include additional components such as an input shaft 46, for connection to a rotational energy source via the device input shaft 44, i.e. torque, a clutch 48 (see FIG. 8), which is used to mechanically couple a rotational source/load from the device, or a gearbox, which is used to match the device RPM to the source or load requirements. The housing 42 may include a series of apertures 50, through which bolts, or other fastening means (not shown), are placed to assemble and secure components together.

FIG. 5 is a cross sectional view of a portion of the multi-cluster hydraulic gear device 20. The three gear device 23 multi-cluster arrangement includes three secondary gears 24 located about, and engaging with, the periphery of a central main gear 22. Ports 40 are located about each secondary gear 24 and are operable to allow for fluid flow there through. FIG. 6 is an external perspective view of the multi-cluster hydraulic gear device 20 enclosed within the housing 42, with port 40 apertures shown in the housing 42.

FIG. 7 illustrates one embodiment of the multi-cluster hydraulic gear device 20, in use as a motor that may be used in an application such as a crane, for hoisting a load. FIG. 7 shows the multi-cluster hydraulic gear device 20 in housing 42 connected to a winch drum 52. The multi-cluster gear device 20 can be used in motor mode to hoist the load and, when required, can be used as a brake, i.e. in pump mode, when the load is lowered. This example serves as one application for the use of the multi-cluster hydraulic gear device 20 described herein.

FIG. 8 shows a further embodiment of the multi-cluster hydraulic gear device 20, and in particular the use of the device 20, described herein. In this embodiment the device 20 includes several gear cluster devices 23 with the secondary gears 94 located on the inside of the main gear 92. The illustrated embodiment includes four secondary gears 94, of which two can be seen in FIG. 8. The embodiment shown illustrates the use of the multi-cluster gear device 20 in a towed vehicle. The use will be described further below.

FIG. 9 illustrates one example of the hydraulic circuitry of the four external gear cluster system similar to FIG. 8 but with the secondary gears located externally relative to the main gear. As can be seen in FIG. 9, fluid is operable to flow from one external secondary gear, 24, to the adjacent external small gear. FIG. 9 includes a series of arrows showing direction of fluid flow. Each arrow includes the portion (e.g. %) of fluid that flows along the path taken from the original total (e.g. 100%) fluid input. As described above, a portion (e.g. 50%) of the total fluid flow for each secondary gear is carried around each secondary gear and the remaining portion (e.g. 50%) is carried by the main gear and carried to the adjacent secondary gear where it combines with the portion (e.g. 50%) that has been carried around the adjacent secondary gear to output at as the total (e.g. 100%) output for that gear cluster 23 (see FIG. 8). Each secondary gear 24, is able to draw its own source of fluid, from a fluid reservoir indicated by arrows showing input of total (e.g. 100%), of which the portion (e.g. 50%) rotates around the small gear and remaining portion (e.g. 50%) of which is carried to the adjacent secondary gear 24 via the main gear.

For example, as seen in the figure, the portion (e.g. 50%) of the fluid that is drawn into the low pressure side, shown at 1A, of the top secondary gear 24-1, is carried around the secondary gear 24-1 and is carried over to 1B. The remaining portion (e.g. 50%) is carried over to 2B by the main gear 22 where it joins with portion (e.g. 50%) that has passed around the small secondary 24-2 to result in port output total (e.g. 100%) at the high pressure side 2B. The inlet fluid drawn by 2A, see arrows at 2A, is divided into two parts by the related gear cluster device 23, i.e. the secondary gear 24-2 and the main gear 22. Portion (e.g. 50%) of the drawn fluid follows the secondary gear 24-2 around to the high pressure side 2B, as indicated by the direction of the arrow around the secondary gear, where it combines with the portion (e.g. 50%) from secondary gear 24-1, as discussed above. The other portion (e.g. 50%) is carried by the main gear 22 over to the high pressure side of the adjacent secondary gear 24-3, indicated at 3B. Likewise, inlet fluid is drawn by 3A, see arrows at 3A, and is divided into two parts by the related gear cluster device 23, i.e. the secondary gear 24-3 and the main gear 22. Portion (e.g. 50%) of the drawn fluid follows the secondary gear 24-3 around to the high pressure side 3B, as indicated by the direction of the arrow around the secondary gear 24-3, where it combines with the portion (e.g. 50%) received via the main gear 22 from secondary gear 24-2. The other portion (e.g. 50%) is carried by the main gear 22 over to the high pressure side of the adjacent secondary gear 24-4, indicated at 4B. The fluid flow at secondary gear 24-4 is as per the above. Fluid is drawn in at low pressure side 4A. Of this inlet fluid, portion (e.g. 50%) is carried by secondary gear 24-4 around to the high pressure side 4B, where it merges with the portion (e.g. 50%) received from secondary gear 24-3. The remaining portion (e.g. 50%) is carried by main gear 22 to the high pressure side 1B of secondary gear 24-1 to combine with the portion (e.g. 50%) that has been carried around secondary gear 24-1. Each high pressure side, 1B, 2B, 3B and 4B is therefore releasing respective port output total fluid (e.g. 100%) at fluid pressures higher than the inlet fluid pressures.

The total output of the system illustrated in 9 is therefore able to deliver the output flow equivalent of four pump pairs (i.e. 8 gears) using only 5 gears associated with 4 gear devices 23 in a common gear cavity 25, within the multi-cluster hydraulic gear device 20.

As can be seen, check valves, indicated generally at 30, and solenoids, indicated generally at 32, may be located within the fluid lines. Check valves may be located on the high pressure line, as seen in FIG. 9. The inclusion of a solenoid valve 32, at each gear 24 allows for flow of hydraulic fluid cycling back through the rotating gear 24, as opposed to out of the multi-cluster hydraulic gear device 20.

Reference will now be made to FIG. 8 in which one embodiment of the use of the multi-cluster hydraulic gear device 20 in a vehicle brake system is shown.

The following description of one use of the multi-cluster hydraulic gear device 20, described above, is provided as an example only and is not meant to be limiting to the application of the multi-cluster hydraulic gear device 20 described herein. For the purposes of this description, the use of the multi-cluster hydraulic gear device 20 will be described herein in reference to its use as a gear pump in a vehicle braking system. Examples of the types of vehicles that it may also be used in include, but are not limited to, rail applications over the road tractors, trailers, city buses, heavy duty commercial vehicles, light duty commercial and passenger vehicles.

The multi-cluster hydraulic gear device 20 includes an outer case 80 that is connected to a rotating towing or towed vehicle wheel. The device 20, used in a pump mode in this example, includes spur gears, or small gears, 94, which are fixed within a stationary housing 83 located inside the outer case 80. When braking is invoked, pilot fluid is injected into the clutch cylinder 82, which moves the clutch block 84 radially outward to engage with the rotating outer case. This action results in engagement of clutch plate 87 to the rotating outer case 80. Following this, clutch plate 87 starts to rotate mechanical drive gear 88, which is mechanically connected to clutch plate 87. This in turn spins all four mechanical spur gears 90, which are each connected to one of four small hydraulic spur gears, or secondary gears 94. The secondary gears 94 are as per the secondary gears 24 described above. Each of the secondary gears 94 in turn is connected to, and passively rotate, the ring gear, or main gear, 92. The main gear 92, is as per the main gear 22 described above. This initiates pumping action and fluid is drawn from a reservoir to the pump ports, not shown, at the meshing point. A partition wall 96 is positioned between the mechanical and hydraulic zones and is fitted with seals isolating the two compartments and the fluid.

Braking effort may be modulated by controlling (i) the displaced volume, i.e. how many pumps are activated; and (ii) the pressure head. When the fluid leaves the control valve, it may be sent to a filter for cleaning and a heat exchanger to dissipate kinetic brake energy before it is recirculated back to the pump. When the clutch is engaged to initiate fluid flow, all the secondary gears 94 begin to rotate, transferring fluid in direct proportion to their rotational speed and size. Total braking effort can then be modulated by a combination of two modes (i) step modulation and/or (ii) analog modulation.

In step modulation, opening of bypass solenoid(s) enables the individual pumps output by “shorting” fluid flow. In the case of the illustrated four pump cluster, seen in FIG. 9, flow volume at levels of more than 0 to 100% of total can be invoked. This technique is sometimes referred to as “staircase modulation” owing to its stepped nature. In analog modulation, by electronically modulating head pressure generated by the control valve, brake effort can be continuously varied, creating infinite intermediate control levels between the stepped values. By synchronizing commands between the two modes, “bumpless” transition between steps can be achieved.

FIG. 10 is a schematic of a by-pass loop. As described earlier each pump “hands off” portion (e.g. 50%) of its total intake to the nearest cluster device 23, the handoff direction dictated by pump rotational direction. When a valve is opened to “short” hydraulic flow, the fluid does not simply loop locally. Fluid is drawn from a fluid reservoir, at the interface of pump A and the drive gear 22, shown at arrow A. Portion (e.g. 50%) of the fluid follows pump A, as it rotates, to the high pressure side, shown at arrow B.

The working pump A continuously pushes a portion (e.g. 50%) flow volume, of the fluid drawn in, to the bypassed pump B via drive gear 22, i.e. portion (e.g. 50%) is carried by drive gear 22 to pump B. An initial fluid is drawn into the low pressure side of Pump B, at position C, of this portion (e.g. 50%) is carried by the drive gear 22 to join with the portion (e.g. 50%) carried around pump A to result in total fluid output. Of the fluid drawn in at position C, portion (e.g. 50%) follows pump B around to meet with the portion (e.g. 50%) that has been passed from working pump A. The combined portions are then recirculated through the cluster. The net effect: the bypass solenoid has shorted out pump B and the circuit behaves as if that pump simply does not exist. Instead of outputting portion (e.g. 50%) of the fluid, the fluid is simply recirculated within pump B via the solenoid. In other words, the portion (e.g. 50%) volume has simply passed through as though pump B were not there. It will therefore be clear that every cluster that is in the bypass mode will always a fresh injection of portion (e.g. 50%) of cooled oil with every revolution. One advantage of the injection of fresh oil in the bypass mode is for cooling purposes of the overall device 20 and/or for respective gear devices 23 adjacent to the bypassed gear device 23.

Referring to FIG. 10, shown is that inlet fluid A is split into fluid portions A1 and A2 and inlet fluid C is split into fluid portions C1 and C2. As pump A is not in bypass mode, the secondary gear of pump A carries fluid portion A1 over to output port B and main gear 22 carries fluid portion C2 over to output port B, thus providing for total output at port B of combined fluid portions C2 and A1. In terms of bypassed secondary gear/pump B, inlet fluid portion C1 is carried around by the secondary gear to meet incoming fluid portion A2 carried by main gear 22. These two portions then meet and combine as portions C1+A2 and flow via the bypass valve 9 over to inlet port C. Next, a portion of the combined C1+A2 is directed as new portion C2 and the remainer is drawn from the reservoir as new portion C1. When bypass valve 9 is opened, as described, the fluid will take the path of least amount of resistance. In other words, given that pump A is working it is understood that a control valve 8 can be partially closed, thus offering a flow restriction for the output of gear device A in FIG. 10. The fluid will therefore have an easier time flowing via the bypass valve 9 than via the flow restriction offered by control valve 8. Fluid will therefore flow or otherwise partially recirculate (e.g. portion C1 carried by secondary gear first to meet portion A2 and then back through valve 9 to inlet port C) in the bypassed gear device 23 and not to the output port (not shown where A2 and C1 meet) of the bypassed pump B. It is noted that every gear device 23 can have a respective bypass valve 9 associated therewith, thereby providing for the passage of fluid directly from the outlet port 40 of the gear device 23 directly to the input port 40 of the gear device 23, for use as part of the next draw of fluid into and processed by the bypassed gear device 23.

Therefore, in situations where higher hydraulic pressure with reduced fluid flow rates (e.g. fluid volume) is desired as total fluid output from the device 20, bypass valve(s) 9 are opened for one or more respective gear devices 23 so that the remaining working (e.g. pumping) gear device(s) 23 (those gear devices 23 not in bypass mode) can be used to provide the hydraulic higher pressure total fluid output. It is recognized that the terms higher and lower are relative to the gear device 20 working in non-bypass mode or otherwise having a greater number of gear devices 23 in non-bypass mode, as compared to the higher pressure and reduced volume provided by the remaining gear devices 23 that are hydraulically coupled to the total output of fluid from the gear device 20.

As noted, the gear device 20 can contain multiple gear devices 23 with respective by pass vales 9, such that selective bypass (via bypass valve 9 operation) of each gear device 23 within the gear device 20 can be implemented via operational control of the respective bypass valve 9 of the respective (i.e. associated with) gear device 23. It is also recognized that one bypass valve 9 can be associated with and therefore control the bypass mode with two of more gear devices 23, as desired. Another way to define bypass valve 9 operation is that bypass valve(s) 9 can be used to either engage hydraulically (via valve 9 close to block fluid flow there-through) or disengage hydraulically (via valve 9 open to allow fluid flow there-through) the respective associated gear device(s) 23 from the other gear device(s) 23 of the gear device 20.

Therefore, in effect the use of the bypass valve(s) 9 provides for hydraulic decoupling of the associated gear device(s) 23 from the total output flow of the device 20 while at the same time providing for the associated gear device(s) 23 to remain mechanically coupled in the gear cavity 25 with all of the other gear devices 23 contained therein. This is advantageous for gear cooling and lubrication purposes.

This can be repeated for more than one pump provided each includes a solenoid valve (e.g. bypass valve 9), or any other means that allows a pump gear cluster to be by-passed from the total number of gear devices/clusters 23 of the gear device 20, and allows for repeated flow of the fluid within pump B. Since pumps 23 are mechanically geared together, displacement can be identical and portion (e.g. 50%) of each input is passed to the nearest pump 23 output, limited pressure head can be generated and the serial handoff can occur at minimal pressure. Upon finally arriving at a “working pump” 23, the carried portion (e.g. 50%) joins the awaiting portion (e.g. 50%), and total combined portions exit (positive displacement device). Pressure output of the gear device 23 can be dictated by the control valve 8 setting. It will be understood that when the multi-cluster gear device 20 is engaged, if only one gear cluster device 23 is working, the by-pass loop allows for the rest of the gears to be kept lubricated and therefore cooled, i.e. whenever a situation arises where one or more pump gear cluster devices 23 is not working the gears do not run dry. In addition the gears are kept cool by continuous fluid flow.

In one embodiment, shown in FIG. 11, more than one multi-gear cluster device 20 may be used at one time. FIG. 11 shows a first housing 99, containing a multi-gear cluster showing the secondary gears 24, and a second housing 101, showing another multi-gear cluster including a main gear 22 connected to a common main shaft 104 and secondary gears 24 connected to common shafts 100. In such an embodiment, the multi-gear cluster devices would be mechanically connected together, e.g. along the one drive shaft or other shaft. Each device 20 may be connected to a source of hydraulic fluid independently of the adjacent device 20. The total volume output of the aggregated devices would be cumulative, i.e. the sum of the output of the individual devices 20. The advantage of using the device 20 in this configuration is that it allows for a greater overall output based on the use of a series of multi-cluster devices versus using a series of two gear pumps. In other words, if two multi-cluster gear devices are used, each having a four cluster configuration, the total output is equivalent to 8 two gear traditional pumps. The output is reached using only 10 gears compared with 16 that would be used in the traditional pump arrangement. This means that the space requirement of the multi-cluster gear device is smaller compared to the traditional two gear pumps. In addition, less components generally means reduced RPM and less overall maintenance required.

Alternative Embodiments of Multi-Cluster Hydraulic Gear Device 20

Referring to FIG. 12, shown is a multi-cluster hydraulic gear device 20 showing an open gear cavity 25 of the housing 42. Ports 40 on either side of their respective gear devices 23 provide for ingress and egress of fluid through the housing with respect to gear cavity 25. The present embodiment shows a three gear hydraulic gear device 20, however other gear numbers are contemplated, such that the number of gears is less than double the number of gear devices 23 contained within the multi-cluster hydraulic gear device 20 (e.g. in the three gear case shown, three gears is less than 2 times 2 gear devices 23). Further, it is recognised that in order to inhibit blow-by effects, tolerances (e.g. clearance TOL) between a radial distal end surface 107 of teeth 108 and the adjacent inner surface 110 of the gear cavity 25 is minimized. Example clearance TOL are ½ to 1 thousandth of an inch. Further, as is shown in FIG. 14 a, the distance TOL is used to provide for a minimized spaced apart configuration of the radial distal end surface 107 of teeth 108 with the adjacent inner surface 110 of the gear cavity 25, so as to inhibit contact between the radial distal end surface 107 of teeth 108 with the adjacent inner surface 110 to minimize the blow-by effect within a clearance zone 120. It is recognised that practically, portions of the circumference of the gear are spaced apart from the inner surface 110 by a distance greater than the clearance TOL, particularly in those regions outside of the clearance zone 120, for example where meshing of gear teeth between adjacent gears 102,106 occurs as well as in port regions when the ingress and egress of hydraulic fluid occurs. It is recognised that the gear cavity 25 contains respective gear chambers, two for each of the gear devices 23, e.g. one low pressure and one high pressure chamber associated with the respective port 40.

Due to separation distances between shafts 100 for the secondary gears 102, in order to accommodate the main gear 106 positioned on shaft 104 between the two secondary gears 102, and potential unequal hydraulic pressures at the respective fluid ports 40, the gears 102 and/or the gear 106 can be forced away from one of their respective ports 40 and towards the other of their respective ports 40 due to a differential in port pressures, i.e. the respective gear(s) would be forced in a direction lateral to the longitudinal axis of their shaft 100,104 For example, where the multi-cluster hydraulic gear device 20 is used as a pump, then inlet port A would be at a lower pressure than outlet port B and thus secondary gear 102 there-between would be forced or otherwise biased by the fluid pressure differential of the ports A, B laterally away from port B and towards port A. In the present three gear example, the rotations of the gears is such that inlet port D would be at a lower pressure than outlet port C and thus secondary gear 102 there-between would also be forced or otherwise biased by the fluid pressure differential of the ports C, D laterally away from port C and towards port D. Thus it can be seen for some configurations of the multi-cluster hydraulic gear device 20, each port side of the gear cavity 25 includes both a high pressure port and a low pressure port. In other words, each port side of the gear cavity 25 includes both an inlet port and an outlet port.

A consequence of the lateral movement of the secondary gears 102 with respect to their longitudinal axis is that the separation clearance TOL is reduced (see FIG. 14 b), as the distal ends 107 of the teeth 108 are shifted (or otherwise pushed or drawn) closer towards the adjacent inner surface 110 of the gear cavity 25 during operation of the multi-cluster hydraulic gear device 20. Accordingly, when the separation clearance TOL is reduced to zero, any further shift will result in undesirable contact between the distal ends 107 of the teeth 108 and the adjacent inner surface 110, as the gears 102, 106 rotate, thus causing abrasive wear of the teeth 108 material and/or the adjacent inner surface 110 material. It is recognised that during operation of the multi-cluster hydraulic gear device 20, the actual separation clearance TOL can vary due to variability in pressure input (and/or output) of the fluid ports, thus causing variability in the pressure differential between opposing ports A, B or C, D. For example, the variability in pressure differential can be caused due to variations in rotational speed of the gears 102,106 or can be caused due to variations in inlet and/or outlet hydraulic fluid pressures due to variable operation of other hydraulic devices (e.g. line valves opening/closing and/or changing hydraulic load device or supply device conditions) connected via hydraulic lines with the ports 40. Thus a spike in normal operating fluid pressure (e.g. during a braking condition when the device 20 is used in a hydraulic braking system) can cause temporary contact between the teeth 108 material and/or the adjacent inner surface 110 material due to a sudden and transient increase in differential fluid pressures.

One mechanism to provide for acceptable material wear inside of the gear cavity 25 is to use a disposable (e.g. replaceable) sleeve 112, which is inserted via cavity face 115 of the gear cavity 25, between an inner surface 118 of the housing 42 body forming the gear cavity 25 and the distal ends 107 of the teeth 108 of the gears 102, 106. In this case the inner wall 118 located in the clearance zone 120 is positioned a combined distance of a thickness T of the sleeve 112 and the clearance TOL away from the nearest portion of the radial distal end surfaces 107 of the teeth 108, of the respective gear 102, 106. The inner surface 110 material of the sleeve 112 is selected so that if, and when, the distal ends 107 of the teeth 108 contact the inner surface 110, the material of the sleeve 112 is preferentially abraded over the material of the teeth 108. One advantage to using the sleeve 112 is that it can be replaced with excessive wear and can be a relatively low cost part compared to replacing damage or wear to the precision machined housing 42 itself (e.g. in the extreme case damage directly to the housing inner surface of the gear cavity 25 can require replacement of the entire machined housing 42). For example, the material of the sleeve 112 can be made of a material that is metallurgically softer than the material of the gear teeth themselves. Otherwise, the material of the gear teeth is of a different hardness (e.g. harder) than that of the material of the sleeve 112.

Sleeve 112 can be comprised of ductile material (e.g. iron) that will wear away preferably as a particulate (e.g. powder) rather than as shavings. In general, sleeve 112 preferably wears away as a powder rather than shavings, which can be destructive to the internal components (e.g. gears 102,106) of device 20. In some embodiments, sleeve 112 can be comprised of an oil-impregnated alloy, including copper or iron alloys, for example, that help reduce friction and wear between gears 102,106 and sleeve 112. Other examples of the sleeve 112 material can be sintered materials. These sintered materials are initially powder material held in a mold and then heated to a temperature below the melting point so that the atoms in powder particles diffuse across the boundaries of the particles, thus fusing the particles together and creating one solid piece as the sleeve 112. As noted, sleeve 112 has tight tolerances with gears 102 and gear 106 with respect to the inner surface 110. Tight tolerances using clearance TOL with sleeve 112 increases the efficiency of the gear device action of gear 102 and gear 106 to inhibit blow-by fluid loss between the gears 102,106 and interior surface 110 of housing 42, which would decrease the operational efficiency (e.g. pump efficiency) of the device 20. Sleeve 112 can include fluid apertures 41 that align with fluid ports 40 of the housing 42.

In terms of coupling of the sleeve 112 with the gear cavity 25, the sleeve 112 can be press fit (e.g. friction fit) into the gear cavity 25. Alternatively, or in addition to, the sleeve 112 can be fastened by a plurality of releasably secure fasteners 116 (see FIG. 13), including examples such as but not limited to pins, threaded fasteners, etc., thus securing the sleeve 112 to the body of the housing 42. It is recognised that movement of the sleeve 112 within the gear cavity 25, relative to the body of the housing 42, can be undesirable due to the close tolerances of the tolerance clearance TOL.

In some embodiments, sleeve 112 can have a non-uniform thickness. For example, a portion (or portions) of sleeve 112 that is/are subject to increased wear may have increased thickness over that of adjacent portions, so that sleeve 112 can have a longer service time before requiring replacement due to wear.

A hydraulic system can also be used to measure wear of sacrificial sleeve 112. As sleeve 112 becomes more worn the efficiency of the device 20 action of gears 102,106 decreases of the gear devices 23. By measuring fluid flow relative to RPM of the drive shaft that is coupled to gears 102,106, the hydraulic system can measure the efficiency of device 20 and thus wear of sleeve 112. Hydraulic system can be coupled to a vehicle data bus to indicate a service requirement for the sleeve 112.

In some embodiments, sleeve 112 can be a partial sleeve 114 (or sleeves) that does/do not completely surround all of the distal radial surface ends 107 of the teeth 108 of gears 102,106, rather covers all or a portion of the interior surface 118 of the gear cavity 25 extending about the distal ends 107 of the teeth 108 in the clearance TOL zone 120 (see FIG. 14 a). For example, referring to FIG. 13, the sacrificial sleeve 112 has a plurality of sleeve portions 114-1, 114-2, 114-3, 114-4, such that four sleeve portions 114 are shown, however it is recognised that one or more portions 114 can be used as desired. The partial sleeves 114 can be positioned in the gear cavity 25 between the interior surface 118 of the housing 42 and the radial distal end surfaces 107 of the teeth 108 of one or more of the gears 102, 106. It is recognised that the individual sleeve portions 114 can extend about all or a portion of the circumference of the gears 102, 106 in the tolerance zone 120. Example portions of this extension can be such as but not limited to: over one half circumference but less than full circumference of the respective gear; up to one half circumference of the respective gear; up to one third circumference of the respective gear; up to one quarter circumference of the respective gear; etc. Further, it is recognised that the partial sleeve 114 may not include the portion of gear cavity surface 118 containing fluid ports 40 because these surface 118 portions are adjacent to the meshing location of the gear teeth 108 and as such would not come into contact with gears 102,106, as greater clearance is provided in these locations for ingress and egress of hydraulic fluid with respect to the gear cavity 25.

In particular, the partial sleeve portion 114 can be positioned on the inner wall 118 of the gear cavity 25 and adjacent to the portion of the radial distal end surfaces 107 of the teeth 108 of the respective gear that are configured to have the predefined clearance TOL between the radial distal end surfaces 107 and the adjacent gear cavity 25 surface—e.g. surface 110 when sleeve 114 is used. In this case the inner wall 118 is positioned a combined distance of a thickness T of the inner sleeve portion 114 and the clearance TOL away from the nearest portion of the radial distal end surfaces 107 of the teeth 108, of the respective gear 102, 106. Alternatively, the partial sleeve portion 114 can be used only for a portion of a clearance TOL zone 120 to provide for sacrificial (e.g. predetermined, predefined, preferred) wear surface 110 while the remaining portion of the clearance TOL zone 120 can be provided by a non-sacrificial (e.g. non-predetermined, non-predefined, non-preferred) wear surface 118 of the housing 42 exposed in the gear cavity 25. An example of this configuration is shown in FIG. 14 a, such that an area 120 having the predefined clearance TOL between the radial distal end surfaces 107 of the teeth 108 (not shown for convenience) and the adjacent exposed gear cavity 25 surface (e.g. surface 110, surface 118, combined as surface 118 and surface 110), such that it is recognised that surface 110 is provided in the gear cavity 25 by the sleeve 114 and surface 118 is provided by the housing 42. In this example, it is contemplated that the lateral movement of the gear 102, 106 during hydraulic loading is designed to move (and potentially contact) only the surface 110 rather than the surface 118, as shown in FIG. 14 b.

Referring to FIG. 15, shown is the housing 42 having a series of one or more cavities 122 in the inner wall 118 of the gear cavity 25. One or more of the sleeve portions 114-1,-2,-3,-4 of the segmented sleeve 114 is coupled to a mounting block 120, sized to be received in the respective cavity 122, thus positioning the sleeve 114 portion adjacent to the respective gear 102,106 when the gear 102,106 is installed in the gear cavity 25. The mounting block 120 and sleeve 114 portion 114 can be referred to as a sleeve assembly 123. The mounting block 120 is fastened to housing via a press fit within the cavity 122 and/or by one or more fasteners 116 (e.g. threaded fasteners). The mounting blocks 120 can be integrally attached to the sleeve 114 portions, thus forming an integral sleeve assembly 123. The mounting blocks 120 can also be releasably coupled to the sleeve 114 portions (not shown) using appropriate fasteners, thus forming a multiple component sleeve assembly 123. Further, it is recognised that the material used to manufacture the mounting blocks 120 can be different from the material used to manufacture the sleeve 114 portions of the sleeve assembly 123 and/or gears 102,103. For example, only the sleeve 114 portion of the sleeve assembly 123 can be made of the preferential wear material (e.g. powder forming material) as discussed above. Referring to FIG. 16, shown is an assembly of the segmented sleeve 114 prior to installation of the plurality of gear devices 23 including the plurality of gears 102,106.

Referring to FIG. 17, shown is the sleeve assembly 123 connected to the body of the housing 42 via connecting pin 124, once the mounting block 120 is received in the cavity 122. The pin 124 is inserted via aligned hole 126 in housing 42 with hole 128 in mounting block 120. Also shown is a seal 128 for positioning between the cavity 122 and the mounting block 120, used to inhibit leakage of hydraulic fluid out of the gear cavity 25 via the cavity 122. The pin 124 connection can also be used to provide for pivot of assembly 123 about the pivot point to provide for the sleeve 114 to move out of the way of the advancing gear 102,106 to reduce severity of sleeve 114 wear, due to potential contact between the gears 102,106 and the sleeve 114.

Referring to FIG. 18, shown is an alternative embodiment of the sleeve assembly 123, including a slider block 130 configured to move within the cavity 122 relative to the mounting block 120. Within the sleeve assembly 123, the slider block 130 is connected to the sleeve 114 and the slider block 130 is also movably coupled to the mounting block 120. In this embodiment, the mounting block 120 is fixedly connected to the housing in the cavity 122, such that the slider block 130 is free to move relative (referrer to by arrow RM) to the mounting block 120, thus providing for displacement of the sleeve 114 laterally to the axis of shaft 100,104 of the gear 102,106, as the respective gear 102,106 also is displaced laterally (referred to as LD) due to fluid port pressure differentials as discussed above (see FIG. 12). It is recognised as the gear 102,106 moves towards the sleeve surface 110 (see FIG. 12) clearance TOL is reduced towards contact and therefore biases the sleeve 114 of the sleeve assembly 123 for movement within the cavity 122 in the same direction as the movement (e.g. shifting) of the gear 102,106. This relative movement of the sleeve 114 is advantageous, as the sleeve 114 can move out of the way of the gear 102,106 as the gear 102,106 is laterally displaced due to the pressure differential, thus providing for reduced wear of the sleeve 114. It is recognised that a coupling mechanism 132 (see FIG. 19) between the mounting block 120 and the sliding block 130 provides for relative movement there-between. The cavity 122 (in ghosted view) in the Figure is shown enlarged, in order to illustrate the movement of the slider block 130 therein. Is also recognised that the slider block 130 could be positioned outside of the cavity 122, and thus relative movement of the slider block 130 would not be unduly restrained by the interior walls of the cavity 122.

One example of the coupling mechanism 132 is a tongue 134 and groove 136 connection, such that the tongue 134 is slidably engaged with the groove or channel 136. It is recognised that the tongue 134 can be mounted on the slider block 130 and the groove is positioned in the mounting block 120. Alternatively, the tongue 134 can be mounted on the mounting block 120 and the groove is positioned in the slider block 120. The coupling mechanism 132 can be of a dovetail cross sectional shape, for example.

Referring to FIG. 20, shown is a thrust plate 134 that is positioned between an end face 136 of the housing 42. As an example, the housing is made up out of a number of components 42-1, 42-2, 42-3, coupled together via a number of threaded fasteners 138. The housing components 42-1, 42-3 provide the end faces 136 providing end walls for the gear cavity 25 in the housing portion 42-2. As shown in FIG. 22, the thrust plate is positioned in the gear cavity 25 between the end face 136 and sidewalls 140 (or side face 140) of the gears 102,106, thus providing for a separation clearance TOL2 of clearance approximately similar in magnitude to that of clearance TOL (e.g. ½ to 1 one thousandth of an inch). During operation of the hydraulic gear device 20, hydraulic fluid is allowed to flow between the thrust plate 134 and the end face 136, thus providing for balanced pressure forces to keep the thrust plate 134 from contacting the end surface 136 or the sidewalls 140. The provision of separation clearance TOL2 as a tight tolerance with thrust plate 134 increases the efficiency of the gear device action of gear 102 and gear 106 to inhibit blow-by fluid loss between the sidewalls 140 of the gears 102,106 and the adjacent face of the thrust plate 134. This fluid loss due to blow-by would decrease the operational efficiency (e.g. pump efficiency) of the device 20.

However, as discussed above, due to potential unequal hydraulic pressures in the gear cavity 25 at the respective fluid ports 40, different portions of the thrust plates 134 can be forced away from or towards the nearest adjacent port 40 to the thrust plate 134 portion. A consequence of this biasing of different portions of the thrust plate 134 in respective different directions (e.g. either away from or towards) with respect to their respective adjacent port 40, is that the thrust plate 134 can become warped due to a differential in port 40 pressures. For example, as discussed for FIG. 12, where the multi-cluster hydraulic gear device 20 is used as a pump, then inlet port A would be at a lower pressure than outlet port B and thus the portion of thrust plate 134 nearest port A would be drawn towards port A while the portion of thrust plate 134 nearest port B would be forced or otherwise biased by the fluid pressure away from the port B. In the present three gear example, the rotations of the gears 102,106 is such that inlet port D would be at a lower pressure than outlet port C and thus the portion of thrust plate 134 nearest port D would be drawn towards port D while the portion of thrust plate 134 nearest port C would be forced or otherwise biased by the fluid pressure away from the port C.

Accordingly, one can understand that as this port pressure differences become more manifest due to increased operating pressures, the degree of warp and/or twist of thrust plate 134 can become more and more pronounced. The consequence of warp or twisting of the thrust plate 134 is that due to the tight tolerances of clearance TOL2, the degree of warping of the thrust plate 134 can become such that the clearance TOL2 is breached by the warping and therefore surface 142 opposing the sidewalls 140 of the gears 102,106 can come into contact therewith, thus causing undesirable wearing or abrading of the gear material and/or thrust plate material. The damage caused by this undesirable wear can result in undesirable increases in the clearance TOL2 (due to gear surface 140 wear and/or plate surface 142 wear) as well as damage to the gear teeth themselves due to wear material circulating in the gear cavity 25. This damage can be realaized/expressed as increase in blow-by of the fluid.

Referring again to FIGS. 20 and 21, the tendency of the thrust plate 134 to warp can be inhibited by the use of thrust bearings 144 positioned between the thrust plate 134 and the sidewall 140 of the gear (in this case, by example only shown as gear 106). The thrust bearings 144 can be positioned (e.g. via friction or press fit) in a recess 146 in the face 136 of the thrust plate 134. Thus, where the portion of the face 136 having the thrust bearing 144 moves into contact with the adjacent sidewall 140 of the gear 106, the rollers 148 of the thrust bearing can ride on the surface of the sidewall 140, as the gear 106 rotates, thus inhibiting wear of the sidewall 140 as well as inhibiting further warping of the thrust plate 134. A hardened washer or surface 147 can be optionally provided on the sidewall 140 in the vicinity of contact with the rollers 148 of the thrust bearing 144, to help reduce wear of the sidewall 140 as well as to help reduce drag on the gear 106 operation (e.g. slow down the gear 106 or otherwise introduce unnecessary additional friction forces to rotation of the gear 106). It is recognised that the shafts 100 as well as shaft 104 can be positioned on respective bearings 150 (e.g. roller), which can be mounted (e.g. press fit) into cavities 152 provided in the thrust plate 134 and/or in the housing 42. Distance of the projection of the thrust bearing 144 from surface of the thrust plate can be similar to clearance TOL2, this providing for non-contact between thrust plate surface 134 and the sidewalls 140. It is recognised that the thrust plates 134 can be floating between the face 136 and the sidewalls 140 of the gears 102,106, and thus the thrust plate 134 is not fixedly connected to the housing via any fasteners.

Referring to FIG. 23, shown is a half section of the gear assembly of gears 102,106 with thrust plates 134. Show is an installed thrust bearing 144 in recess 146, and hardened surface or washer 147 configured for coming into contact and providing a riding surface for the rollers 148. Noted are the shafts 100, 104 that fit through apertures 156 of the thrust plates 134, such that sides of the shaft 100,104 are free to move/rotate within the aperture 156.

Referring to FIG. 24, shown is a thrust plate assembly 160 that is fixedly connected to the housing 42 via the fasteners 162, for example as a sandwich design between housing portions 42-2 and 42-1 (not shown) or 42-3. It is also recognised that housing portion 42-1 (see FIG. 20) could be replaced by a gearbox housing (not shown), as desired. In this case, the shafts 100, 104 are mounted on an interior portion (e.g. race) 164 of bearings (e.g. roller) 166, and an exterior portion 168 (e.g. cage) of the bearings 166 is mounted in respective cavity 170 of the thrust plate assembly 160. It is recognised that the area of surface 142 of thrust plate 134 is less than area of surface 172 of the end housing portion 42-3 adjacent to the thrust plate assembly 160. This configuration is advantageous, as the force Fin (due to hydraulic pressure of the gear device fluid) directed inwards towards and acting on the thrust plate assembly 160 is greater than a force Fout (due to hydraulic pressure of the gear device fluid) directed outwards towards and acting on the thrust plate assembly 160. As such, this configuration of differential surface areas provides for a net inward force of the thrust plate assembly 134 towards the gears 102,106 and thus helps to relieve hydraulic bias of the thrust plate assembly 160 movement away from the gears 102,106 which would result in an increase in the clearance TOL2.

Referring to FIGS. 25 and 26, in order to help maintain the axial position of the gears 102, 106 on their longitudinal axes, one example mechanism are bushings 176 having a shoulder 178 thereon, which seats up against a sidewall 180 of the bearings 166. Alternatively, the shoulder 178 could be positioned (e.g. machined) directly on the shaft 100, 104 upon which the gear 102, 106 is mounted. It is recognised that each of the gears 102,106 could be mounted on shafts 100,104 having the shoulders 180. It is recognised that each of the gears 102,106 could be positioned adjacent to (or otherwise have bushings 176 integrally made with the gears 102,106) on shafts 100,104, such that it is the bushings 176 having the shoulders 180.

Referring again to FIG. 21, it is recognised that housing portions 42-2 and 42-3 could be integrally machined out of one piece of material as housing 42, such that integral housing portions 42-2 and 42-3 are not connected to one another by threaded fasteners as is the case in the housing 42 configuration of the device 20 of FIG. 24. As such, the thrust plate 134 could be configured as a floating design between the gears 102,106 and the end face 136 of the integral housing portion 42-3 (not shown), which is similar to the face 136 of separate housing portion 42-3 of FIG. 20. Further, the thrust plate 134 position in the integral housing 42 of FIG. 21 is similar to that shown in FIG. 20.

Alternatively, the housing portions of thrust plate assembly 160 and housing portion 42-2 (see FIG. 24) could be integrally machined out of one piece of material as housing 42. This configuration would also result in a fixed configuration (i.e. non-floating) for the thrust plate situated in the integrated thrust plate assembly 160 and housing portion 42-2.

While this invention has been described with reference to illustrative embodiments and examples, the description is not intended to be construed in a limiting sense. Thus, various modification of the illustrative embodiments, as well as other embodiments of the invention, will be apparent to persons skilled in the art upon reference to this description. It is therefore contemplated that the appended claims will cover any such modifications or embodiments. Further, all of the claims are hereby incorporated by reference into the description of the preferred embodiments.

Any publications, patents and patent applications referred to herein are incorporated by reference in their entirety to the same extent as if each individual publication, patent or patent application was specifically and individually indicated to be incorporated by reference in its entirety. 

1. A multi cluster gear device comprising: a shaft rotatable about a longitudinal axis; a primary gear mounted on the shaft; at least two secondary gears spaced about and positioned to engage with the primary gear; each of the at least two secondary gears configured to independently receive fluid from a fluid reservoir and to allow flow of a portion of the fluid about the secondary gear and to allow the remaining portion of the fluid to be carried by the primary gear to the adjacent secondary gear.
 2. A multi cluster gear device comprising: a primary gear; at least two secondary gears spaced about and positioned to engage with the primary gear; each of the at least two secondary gears configured to independently receive fluid from a fluid reservoir and to allow flow of a portion of the fluid about the secondary gear and to allow the remaining portion of the fluid to be carried by the primary gear to the adjacent secondary gear.
 3. The multi cluster gear device according to claim 2, wherein the at least two secondary gears are smaller than the primary gear.
 4. The multi cluster gear device according to claim 2, wherein the at least two secondary gears are spaced evenly about the periphery of the primary gear.
 5. The multi cluster gear device according to claim 2, wherein approximately 50% of the fluid received by each of the at least two secondary gears flows around respective secondary gears and the remaining fluid portion is carried to the adjacent secondary gear.
 6. The multi cluster gear device according to claim 2, wherein the each of the secondary gears discharges approximately half of the total volume of fluid received, such that each of the secondary gears is associated with an input port and an output port, providing for a pair of ports per said each of the secondary gears.
 7. The multi cluster gear device according to claim 6, wherein the gear device includes a third secondary gear engaged with the primary gear, the third secondary gear also having the pair of ports.
 8. The multi cluster gear device according to claim 2, wherein each of the secondary gears is independently fluidly connected to a fluid inlet and a fluid outlet.
 9. The multi cluster gear device according to claim 1, wherein the shaft is driven by a driving source and the multi cluster gear device is operable to function as a pump.
 10. The multi cluster gear device according to claim 1, wherein the shaft is driven by the rotation of the primary and secondary gears.
 11. The multi cluster gear device according to claim 2, wherein the at least two secondary gears are configured to receive fluid at low pressure.
 12. The multi cluster gear device according to claim 1, wherein at least one of the at least two secondary gears are configured to receive fluid at high pressure.
 13. The multi cluster gear device according to claim 1, comprising four secondary gears.
 14. The multi cluster gear device according to claim 1, comprising three secondary gears.
 15. The multi cluster gear device according to claim 1 further comprising a removable sleeve positioned in a gear cavity of a housing containing the primary and secondary gears, the sleeve positioned between an interior wall of the gear cavity and distal radial end surfaces of gear teeth of one or more of the primary gear and the secondary gears.
 16. The multi cluster gear device according to claim 15, wherein the sleeve is provided as one or more sleeve segments.
 17. The multi cluster gear device according to claim 16, wherein the sleeve segment is positioned around one of the secondary gears in a zone having a predefined blow-by gap clearance.
 18. The multi cluster gear device according to claim 17, wherein the sleeve segment is positioned around a portion of the zone and the interior wall of the housing makes up the remaining portion of the zone.
 19. The multi cluster gear device according to claim 15 further comprising a slider block of the sleeve to provide for movement of the sleeve in a direction lateral to a longitudinal axis of the secondary gear.
 20. The multi cluster gear device according to claim 15 further comprising a slider block of the sleeve to provide for movement of the sleeve in a direction lateral to the longitudinal axis of the primary gear.
 21. The multi cluster gear device according to claim 15, wherein the sleeve is comprised of a material that degrades as a powder.
 22. The multi cluster gear device according to claim 21, wherein the material is a layer positioned on a main body of the sleeve.
 23. The multi cluster gear device according to claim 1 further comprising a thrust plate positioned and floating between an end wall of a housing of the device and sidewalls of the primary gear and the secondary gears, and further comprising a thrust bearing positioned between the thrust plate and the sidewall of at least one of the primary gear and the secondary gears.
 24. The multi cluster gear device according to claim 23, wherein the thrust plate is comprised of a material that degrades as a powder.
 25. The multi cluster gear device according to claim 24, wherein the material is a layer positioned on a main body of the thrust plate.
 26. The multi cluster gear device according to claim 2 further comprising a thrust plate positioned between an end wall of a housing of the device and the sidewalls of the primary gear and the secondary gears and further comprising a thrust bearing positioned between the thrust plate and the sidewall of at least one of the primary gear and the secondary gears.
 27. The multi cluster gear device according to claim 26 further comprising a hardened surface on the sidewall adjacent to the thrust bearing.
 28. The multi cluster gear device according to claim 1 further comprising a thrust plate positioned fixedly between an end wall of a housing of the device and sidewalls of the primary gear and the secondary gears.
 29. The multi cluster gear device according to claim 28 further comprising one or more shoulders positioned with respect to the sidewalls of one or more of the primary gear and the secondary gears, the one or more shoulders for abutting a respective bearing portion mounted between the respective gear and the thrust plate.
 30. The multi cluster gear device according to claim 29, wherein the shoulder is provided by a bushing that is positioned between the respective gear and the bearing portion.
 31. The multi cluster gear device according to claim 29, wherein the shoulder is provided by a portion of the gear that contacts the bearing portion.
 32. The multi cluster gear device according to claim 29, wherein the shoulder is provided by a shaft upon which the respective gear is mounted.
 33. The multi cluster gear device according to claim 1 further comprising a thrust plate positioned between an end wall of a housing of the device and the sidewalls of the primary gear and the secondary gears, the end wall having a face with a first surface area exposed to pressurized hydraulic fluid such that the first surface area is greater than a second surface area of a face of the thrust plate also exposed to the pressurized hydraulic fluid, thus providing for a net inward force on the thrust plate towards the sidewalls.
 34. The multi cluster gear device according to claim 28, wherein a gear cavity containing the primary and the secondary gears is positioned in the housing, the thrust plate and the gear cavity integral to the housing as a one piece construction.
 35. A multi cluster gear device comprising: a shaft rotatable about a longitudinal axis; a primary gear mounted on the shaft; a pair of secondary gears spaced about and positioned to engage with the primary gear; wherein the primary gear and the secondary gears define a pair of gear devices for moving hydraulic fluid within a common gear cavity defined by a housing of the gear device.
 36. The multi cluster gear device of claim 36 further comprising at least one additional secondary gear engaging with the primary gear to define another gear device in the common gear cavity, such that a number of ports providing communication of fluid into and out of the gear cavity is less than double the number of the gears within the common gear cavity.
 37. A multi cluster gear device comprising: a primary gear; a pair of secondary gears spaced about and positioned to engage with the primary gear; wherein the primary gear and the secondary gears define a pair of gear devices for moving hydraulic fluid within a common gear cavity defined by a housing of the gear device. 